1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus that include an electrophotographic photosensitive member.
2. Description of the Related Art
Electrophotographic photosensitive members include various materials as charge generation materials. Among such materials, phthalocyanine pigments having high sensitivities are often used as charge generation materials for electrophotographic photosensitive members.
However, when the content of a phthalocyanine pigment in a photosensitive layer or a charge generation layer of an electrophotographic photosensitive member is increased in order to increase the sensitivity, dark attenuation tends to increase. The dark attenuation is a phenomenon in which, when a surface of an electrophotographic photosensitive member is charged, a surface potential of the electrophotographic photosensitive member decreases (attenuates) with time in a dark place. A large dark attenuation means that the degree of decrease (attenuation) in the surface potential of an electrophotographic photosensitive member in a dark place is large.
An increase in the dark attenuation causes a decrease in the image contrast, black dots, and background fogging, which may result in a decrease in the image quality.
Japanese Patent Laid-Open No. 2006-72304 discloses a technique in which a complex of a phthalocyanine pigment and an organic electron acceptor is produced by a particular method, and the dark attenuation is reduced by using the complex.
Japanese Patent Laid-Open No. 2008-15428 discloses a technique in which the dark attenuation is reduced by incorporating a particular salt and a particular charge generation material in a photosensitive layer.
However, according to studies conducted by the inventors of the present invention, the techniques disclosed in Japanese Patent Laid-Open Nos. 2006-72304 and 2008-15428 do not sufficiently reduce the dark attenuation in some cases.